From 34530d8532e22afe0026b956ae395ddc666351b3 Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Thu, 26 Feb 2015 19:06:34 +0100
Subject: Enabled `Concatenate` to concatenate a variadic pack of lists *
 analogously to arbitrary list count concatenation in Scheme's `append` **
 implemented for `Concatenate` instead as it fits better with the structure
 between `Append` and `Concatenate`

---
 src/conditional/cond.h           | 12 +++++++-----
 src/list/operation/concatenate.h | 13 ++++++++++---
 src/list/operation/higher/sort.h |  8 +++-----
 test.cc                          | 12 ++++++++++++
 4 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/src/conditional/cond.h b/src/conditional/cond.h
index ca5e46d..4def611 100644
--- a/src/conditional/cond.h
+++ b/src/conditional/cond.h
@@ -9,12 +9,14 @@ namespace tav {
 
 namespace detail {
 
-template <typename Pair>
-using cond_predicate = IsTrue<Car<Pair>>;
-
 template <typename... Branches>
-struct select_cond_branch {
-	using type = Eval<detail::find_variadic<detail::cond_predicate, Branches...>>;
+class select_cond_branch {
+	private:
+		template <typename Pair>
+		using predicate = IsTrue<Car<Pair>>;
+
+	public:
+		using type = Eval<detail::find_variadic<predicate, Branches...>>;
 
 	static_assert(
 		IsPair<type>::value,
diff --git a/src/list/operation/concatenate.h b/src/list/operation/concatenate.h
index a5cbaa6..cf680c1 100644
--- a/src/list/operation/concatenate.h
+++ b/src/list/operation/concatenate.h
@@ -2,16 +2,23 @@
 #define TYPEASVALUE_SRC_LIST_OPERATION_CONCATENATE_H_
 
 #include "append.h"
-#include "higher/remove.h"
 #include "higher/fold.h"
+#include "conditional/if.h"
 
 namespace tav {
 
-template <typename ListOfLists>
+template <
+	typename    Head,
+	typename... Tail
+>
 using Concatenate = Fold<
 	Append,
 	void,
-	ListOfLists
+	If<
+		Boolean<sizeof...(Tail) == 0>,
+		Head,
+		List<Head, Tail...>
+	>
 >;
 
 }
diff --git a/src/list/operation/higher/sort.h b/src/list/operation/higher/sort.h
index 925ab89..51317fa 100644
--- a/src/list/operation/higher/sort.h
+++ b/src/list/operation/higher/sort.h
@@ -29,11 +29,9 @@ class quick_sort {
 
 	public:
 		using type = Concatenate<
-			List<
-				Eval<quick_sort<Comparator, lhs>>,
-				List<pivot>,
-				Eval<quick_sort<Comparator, rhs>>
-			>
+			Eval<quick_sort<Comparator, lhs>>,
+			List<pivot>,
+			Eval<quick_sort<Comparator, rhs>>
 		>;
 };
 
diff --git a/test.cc b/test.cc
index 525afcf..ef0d8c3 100644
--- a/test.cc
+++ b/test.cc
@@ -839,6 +839,18 @@ static_assert(
 	"(concatenate (list (list 1 2) (list 3) (list 4 5 6))) != (list 1 2 3 4 5 6)"
 );
 
+static_assert(
+	std::is_same<
+		tav::List<tav::Int<1>, tav::Int<2>, tav::Int<3>, tav::Int<4>, tav::Int<5>, tav::Int<6>>,
+		tav::Concatenate<
+			tav::List<tav::Int<1>, tav::Int<2>>,
+			tav::List<tav::Int<3>>,
+			tav::List<tav::Int<4>, tav::Int<5>, tav::Int<6>>
+		>
+	>::value,
+	"(concatenate (list 1 2) (list 3) (list 4 5 6)) != (list 1 2 3 4 5 6)"
+);
+
 // list iota
 
 static_assert(
-- 
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